A pop corn kernel is sort of a sealed container the outer coating of which encloses a layer of hard starch as well as core of soft moisture-laden starch. The amount of moisture is 13.5% to 14%, considered optimum for popping. When the kernel is heated within the range of 200◦ to 230◦ Celsius, the moisture turns into so much steam that not only the hard starch gets cooked but the kernel explodes. It virtually turns inside out, so what you see on the outer surface of pop corn is the hard starch. Popping is essentially the action of turning inside out and that is what creates a puffed up flake out of the hard starch.